The Experts below are selected from a list of 1263 Experts worldwide ranked by ideXlab platform
S W Park - One of the best experts on this subject based on the ideXlab platform.
-
analytical modeling of viscoelastic dampers for structural and vibration control
International Journal of Solids and Structures, 2001Co-Authors: S W ParkAbstract:Different approaches to the mathematical modeling of viscoelastic dampers are addressed and their theoretical basis and performance are compared. The standard mechanical model (SMM) comprising linear springs and dashpots is shown to accurately describe the broad-band rheological behavior of common viscoelastic dampers and be more efficient than other models such as the fractional derivative model and the modified power law. The SMM renders a Prony Series expression for the modulus and compliance functions in the time domain, and the remarkable mathematical efficiency associated with the exponential basis functions of a Prony Series greatly facilitates model calibration and interconversion. While cumbersome, nonlinear regression is usually required for other models, a simple collocation or least-squares method can be used to fit the SMM to available experimental data. The model allows viscoelastic material functions to be readily determined either directly from the experimental data or through interconversion from a function established in another domain. Numerical examples on two common viscoelastic dampers demonstrate the advantages of the SMM over fractional derivative and power-law models. Detailed computational procedures for fitting and interconversion are discussed and illustrated. Published experimental data from a viscoelastic liquid damper and a viscoelastic solid damper are used in the examples.
-
methods of interconversion between linear viscoelastic material functions part i a numerical method based on Prony Series
International Journal of Solids and Structures, 1999Co-Authors: S W Park, R A SchaperyAbstract:Abstract An efficient and accurate numerical method of interconversion between linear viscoelastic material functions based on a Prony Series representation is presented and tested using experimental data from selected polymeric materials. The method is straightforward and applicable to interconversion between modulus and compliance functions in time, frequency, and Laplace transform domains. Good agreement is shown between solutions obtained from the method in different domains. A detailed computational procedure and selection of values for parameters involved in the method are presented and illustrated. In particular, the effects of different choices of relaxation and retardation times on the accuracy of the method are discussed. The mathematical efficiency associated with Prony Series representations of both source and target transient material functions is fully utilized. The method is general enough to cover both viscoelastic solids and liquids. The tensile relaxation data from polymethyl methacrylate (PMMA) and the shear storage compliance data from polyisobutylene are used in illustrating the method. In a companion paper ( Schapery and Park, 1998 ) , an extended approximate analytical interconversion method is presented.
R A Schapery - One of the best experts on this subject based on the ideXlab platform.
-
methods of interconversion between linear viscoelastic material functions part i a numerical method based on Prony Series
International Journal of Solids and Structures, 1999Co-Authors: S W Park, R A SchaperyAbstract:Abstract An efficient and accurate numerical method of interconversion between linear viscoelastic material functions based on a Prony Series representation is presented and tested using experimental data from selected polymeric materials. The method is straightforward and applicable to interconversion between modulus and compliance functions in time, frequency, and Laplace transform domains. Good agreement is shown between solutions obtained from the method in different domains. A detailed computational procedure and selection of values for parameters involved in the method are presented and illustrated. In particular, the effects of different choices of relaxation and retardation times on the accuracy of the method are discussed. The mathematical efficiency associated with Prony Series representations of both source and target transient material functions is fully utilized. The method is general enough to cover both viscoelastic solids and liquids. The tensile relaxation data from polymethyl methacrylate (PMMA) and the shear storage compliance data from polyisobutylene are used in illustrating the method. In a companion paper ( Schapery and Park, 1998 ) , an extended approximate analytical interconversion method is presented.
Tammy Haut L Donahue - One of the best experts on this subject based on the ideXlab platform.
-
skeletal muscle tensile strain dependence hyperviscoelastic nonlinearity
Journal of The Mechanical Behavior of Biomedical Materials, 2016Co-Authors: Benjamin B Wheatley, Duane A Morrow, Gregory M Odegard, Kenton R Kaufman, Tammy Haut L DonahueAbstract:Abstract Introduction Computational modeling of skeletal muscle requires characterization at the tissue level. While most skeletal muscle studies focus on hyperelasticity, the goal of this study was to examine and model the nonlinear behavior of both time-independent and time-dependent properties of skeletal muscle as a function of strain. Materials and methods Nine tibialis anterior muscles from New Zealand White rabbits were subject to five consecutive stress relaxation cycles of roughly 3% strain. Individual relaxation steps were fit with a three-term linear Prony Series. Prony Series coefficients and relaxation ratio were assessed for strain dependence using a general linear statistical model. A fully nonlinear constitutive model was employed to capture the strain dependence of both the viscoelastic and instantaneous components. Results Instantaneous modulus (p 0.1). Additionally, the fully nonlinear hyperviscoelastic constitutive model provided an excellent fit to experimental data, while other models which included linear components failed to capture muscle function as accurately. Conclusions Material properties of skeletal muscle are strain-dependent at the tissue level. This strain dependence can be included in computational models of skeletal muscle performance with a fully nonlinear hyperviscoelastic model.
Mir Hamid Reza Ghoreishy - One of the best experts on this subject based on the ideXlab platform.
-
determination of the parameters of the Prony Series in hyper viscoelastic material models using the finite element method
Materials & Design, 2012Co-Authors: Mir Hamid Reza GhoreishyAbstract:Abstract This paper is devoted to the description of a newly developed methodology for the determination of the parameters of the Prony Series in rubber compounds. Four hyperelastic constitutive equations were selected and combined with the Prony equation to describe the hyper-viscoelastic behaviour of a rubber compound. An in-house simple uniaxial tension test was designed and performed on the three rubber strips with the same length and different widths of 1, 2 and 3 cm. The corresponding finite element meshes of these samples were developed using an adaptive meshing technique. The numerical result of the first sample was compared with experimental results of the associated experiment in conjunction with a Nelder–Mead Simplex optimization method to determine the parameters of the Prony equation. These parameters were further used for the simulation of the other two samples to show applicability and repeatability of the developed method. The comparison of the associated force–extension curves with the experimentally measured data of the two samples confirmed the accuracy and reliability of the predicted parameters by this technique.
Antonio Desimone - One of the best experts on this subject based on the ideXlab platform.
-
An anisotropic linear thermo-viscoelastic constitutive law
Mechanics of Time-Dependent Materials, 2018Co-Authors: H E Pettermann, Antonio DesimoneAbstract:A constitutive material law for linear thermo-viscoelasticity in the time domain is presented. The time-dependent relaxation formulation is given for full anisotropy, i.e., both the elastic and the viscous properties are anisotropic. Thereby, each element of the relaxation tensor is described by its own and independent Prony Series expansion. Exceeding common viscoelasticity, time-dependent thermal expansion relaxation/creep is treated as inherent material behavior. The pertinent equations are derived and an incremental, implicit time integration scheme is presented. The developments are implemented into an implicit FEM software for orthotropic material symmetry under plane stress assumption. Even if this is a reduced problem, all essential features are present and allow for the entire verification and validation of the approach. Various simulations on isotropic and orthotropic problems are carried out to demonstrate the material behavior under investigation.
-
an anisotropic linear thermo viscoelastic constitutive law elastic relaxation and thermal expansion creep in the time domain
Mechanics of Time-dependent Materials, 2018Co-Authors: H E Pettermann, Antonio DesimoneAbstract:A constitutive material law for linear thermo-viscoelasticity in the time domain is presented. The time-dependent relaxation formulation is given for full anisotropy, i.e., both the elastic and the viscous properties are anisotropic. Thereby, each element of the relaxation tensor is described by its own and independent Prony Series expansion. Exceeding common viscoelasticity, time-dependent thermal expansion relaxation/creep is treated as inherent material behavior. The pertinent equations are derived and an incremental, implicit time integration scheme is presented. The developments are implemented into an implicit FEM software for orthotropic material symmetry under plane stress assumption. Even if this is a reduced problem, all essential features are present and allow for the entire verification and validation of the approach. Various simulations on isotropic and orthotropic problems are carried out to demonstrate the material behavior under investigation.
